Transmission line modelled in pi-equivalent form according to [1,pp. 44-45] realized using the Impedance and Admittance submodels. For numerical reasons, the R+jX must not be set equal to zero. --- [1] J. Machowski, J.W. Bialek, and J.R. Bumby, Power System Dynamics and Stability, Number ISBN 0-471-97174. Wiley, 1993.